<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    var name = 222;
    var a = {
      name: 111,
      say: function () {
        console.log(this.name)
      }
    }
    var fun = a.say;
    fun(); // 222
    a.say(); // 111

    var b = {
      name: 333,
      say: function (fun) {
        fun()
      }
    }
    b.say(a.say) // 222
    b.say = a.say;
    b.say() // 333
  </script>
</body>

</html>